1. Field of the Invention
The present invention generally relates to a cleaning apparatus, an image forming apparatus including the cleaning apparatus, and a process cartridge including the cleaning apparatus.
2. Description of the Related Art
In these years, there is demand for electrophotographic type image forming apparatuses such as electrophotographic copiers and electrophotographic printers to be smaller in size and lower in cost to efficiently use office environments. Further, there is demand for the electrophotographic type image forming apparatuses to provide higher image quality according to a need to output image data with higher quality, and to realize a longer service life and higher durability in view of economic efficiency and protection of environmental resources.
To provide higher image quality by an electrophotographic type image forming apparatus (simply referred to as an image forming apparatus when not particularly described, hereinafter), a cleaning apparatus to remove toner remaining on a photosensitive body is known. A toner image is formed on a photosensitive body, which is then transferred onto an intermediate transfer medium and a recording medium. However, a part of the toner sometimes remains on the photosensitive body. Toner images are repeatedly formed on the photosensitive body to be transferred onto the intermediate transfer medium and the like. When a part of the toner remains on the photosensitive body, this toner becomes a blot to degrade image quality of the next image formed. Therefore, in many cases, image forming apparatuses have cleaning apparatuses to remove toner remaining on photosensitive bodies.
As a cleaning method of the cleaning apparatus, a cleaning method using a brush and a cleaning method using a blade are widely known. The cleaning method using a blade, by which toner remaining on a photosensitive body is removed by using a small and inexpensive rubber blade, is widely employed in view of cost, the service life of the photosensitive body, and the like.
For example, Patent Documents 1 through 4 disclose techniques to provide favorable cleaning blades. According to Patent Documents 1 through 3, by specifying conditions such as elasticity, a shape, a pressing method, and an applied pressure of a blade member, an effect to remove toner remaining on a photosensitive body is realized. Patent Document 4 discloses a cleaning method to improve removal efficiency of remaining toner by causing a blade to vibrate.
On the other hand, since it became known that it is more effective to use small spherical toner particles for image formation to provide higher image quality, the small spherical toner particles have been used in many electrophotographic type image forming apparatuses. However, there is arising a problem in that it is difficult to remove the spherical toner particles remaining on a photosensitive body. Therefore, a blade with a better removal property of the remaining toner is required.
At a front end part of a blade of a conventional blade type cleaning apparatus, a rubber blade is pressed onto a surface of a photosensitive body as shown in FIG. 7. When the surface of the photosensitive body moves, the front end part of the blade is deformed, being dragged by the movement of the surface of the photosensitive body. Thus, a wedge-shaped space is formed between the front end part of the blade and the surface of the photosensitive body. Such a blade has a sufficient cleaning effect with respect to a ground toner with a low sphericity, which is easily stopped in this space. However, it is difficult to sufficiently remove spherical toner particles with a small particle diameter remaining on the surface of the photosensitive body since the spherical toner particles with a small particle diameter can roll and can go into an innermost part of the wedge-shaped space, and even slip through a contact part between the blade and the surface of the photosensitive body.
Patent Document 5 discloses a cleaning method of removing the spherical toner particles. By the cleaning method of Patent Document 5, there is a predetermined relationship set among the friction coefficient between the front end part of a blade and toner, the friction coefficient between a surface of a photosensitive body and the toner, an adhering force between the toner and the surface of the photosensitive body, a pressuring force of the blade against the toner, and a pressuring angle between the front end part of the blade and the surface of the photosensitive body. According to this relationship disclosed in Patent Document 5, remaining spherical toner particles adhering on the surface of the photosensitive body can be efficiently removed.
Patent Document 1: Japanese Patent Application Publication No. 9-292722
Patent Document 2: Japanese Patent Application Publication No. 5-119686
Patent Document 3: Japanese Patent Application Publication No. 2000-330441
Patent Document 4: Japanese Patent Application Publication No. 2001-66963
Patent Document 5: Japanese Patent Application Publication No. 2005-99125
According to the cleaning method disclosed in Patent Document 5, the spherical toner particles remaining on the surface of the photosensitive body can be removed. However, since quite a lot of parameters are required to be measured or controlled, it is not easy to achieve favorable conditions. Further, according to this cleaning method, an effect of rolling of the spherical toner particles which are stopped between the surface of the photosensitive body and the front end part of the blade is not taken into sufficient consideration. Therefore, unnecessarily strict conditions may be set for removing the remaining toner. When a conventional ground toner having low sphericity is used, an effect to stop the toner by utilizing the effect of rolling may be low. However, when the spherical toner particles roll on the surface of the photosensitive body, it is considered less likely that the spherical toner particles slip through a space between the blade and the surface of the photosensitive body.